The present invention relates to a quick feeding system, and more particularly to a quick feeding system for feeding quick counting pulses to counters used for counting seconds, minutes, hours and the like in an electronic clock of the digital display type.
An example of prior art systems for feeding quick feed pulses to a counter of an electronic clock is illustrated in FIG. 1 attached to the present specification. The prior art system comprises a quartz oscillation circuit 1 including a quartz oscillation element 1a the frequency of which is 6.5 MHz, a first frequency dividing circuit 21 the output frequency of which is 50 Hz, a second frequency dividing circuit 22 the output frequency of which is 10 Hz, a third frequency dividing circuit 23 the output frequency of which is 2 Hz, a fourth frequency dividing circuit 24 the output frequency of which is 1 Hz, an AND gate 3', a quick feed input circuit 4', a switching circuit 6', a seconds counter 71, a minutes counter 81 and an hours counter 91. In this example, a quick feeding to the hours counter 91 is effected.
The output of the frequency dividing circuit 24 of 1 Hz is supplied to a second input of OR gate 63' in the switching circuit 6' through the seconds counter 71 and the minutes counter 81. A quick feed signal HS.sub.1 is produced by switching on a manual switch 42' in the quick feed input circuit 4'. The signal HS.sub.1 is supplied to a chattering preventing delay flip-flop circuit (D-flip-flop circuit) 46', controlled by the output of the frequency dividing circuit 24, which eliminates chattering of the signal HS.sub.1 due to the operation of the manual switch 42'. An output HS.sub.2 ' of the quick feed input circuit 4' is supplied to the switching circuit 6'. The switching circuit 6' supplies either a carry signal from the minutes counter 81 to the hours counter 91 or a quick feed pulse 621' of 2 Hz from the AND gate 3' to the hours counter 91 in accordance with the signal HS.sub.2 ' from the quick feed input circuit 4'. The hours counter 91 counts the incoming clock pulses from the switching circuit 6' and supplies the output signals to a display device 93 through a decoder 92.
The operation of the system of FIG. 1 will now be described with reference to the wave forms illustrated in FIGS. 2A, 2B, 2C and 2D. FIGS. 2A and 2B illustrate the case where the level of the second input signal 631' of the OR gate 63' is "1" and FIGS. 2C and 2D illustrate the case where the level of the second input signal 631' of the OR gate 63' is "0".
If the switch 42' is caused to close a bit prior to the falling edge of the pulse 451' of 1 Hz under the condition when the level of the signal 631' is "1", the signal 911 is caused to fall simultaneously with the falling of the pulse 451'. Accordingly, the hours counter 91 counts "+1" only a very short time (t.sub.s ') after the closing of the switch 42', as illustrated in FIG. 2A. But, if the switch 42' is caused to close a bit after the falling edge of the pulse 451' of 1 Hz under the condition when the level of the signal 631' is "1", the signal 911 is caused to fall at the next falling edge of the pulse 451'. Accordingly, the hours counter 91 counts "+1" after a time "t'.sub.1 ", which is approximately 1 second, from the closing of the switch 42', as illustrated in FIG. 2B.
If the switch 42' is caused to close a bit prior to the falling edge of the pulse 451' of 1 Hz under the condition when the level of the signal 631' is "0", the signal 911 appears after a time t.sub.2 ', which is approximately 0.5 second, from the closing of the switch 42', as illustrated in FIG. 2C. But, if the switch 42' is caused to close a bit after the falling edge of the pulse 451' of 1 Hz under the condition when the level of the signal 631' is "0", the signal 911 appears after a time t.sub.3 ', which is approximately 1.5 seconds from the closing of the switch 42', as illustrated in FIG. 2D.
Therefore, in the prior art system of FIG. 1, the interval from the closing of the switch 42' to the actual quick feeding of the hours counter varies from t.sub.s ', which is approximately zero, to t.sub.3 ', which is approximately 1.5 seconds, in accordance with the relative time of the closing of the switch 42' with respect to the falling edge of the pulse 451' of 1 Hz. As a result, in the case where it is only necessary to increment the hours counter by a few hours is needed, there is a disadvantage in that an excessive number of quick feeding pulses are apt to be supplied to the hours counter 91 so that the hours counter 91 is apt to be excessively incremented.